Security	Date	Code	Shares	Price	A/D	Owned after	D/I	Nature of ownership
Class A Common Shares^{F1,F2,F14,F15}	May 29, 2018	P	299,403	$18.00	A	299,403	I	See Footnotes
Class A Common Shares^{F1,F3,F14,F15}	May 29, 2018	P	2,700,597	$18.00	A	2,700,597	I	See Footnotes

Table II — derivative securities

Security	Conv. / exercise price	Date	Code	Shares	A/D	Exercisable	Expires	Underlying	Underlying shares	Owned after	D/I
Series C Preferred^{F4,F6,F14,F15,F5}	—	Feb 9, 2018	P	420,897	A	—	—	Class A1 Common Shares	420,897	420,897	I
Series C Preferred^{F4,F7,F14,F15,F5}	—	Feb 9, 2018	P	3,734,103	A	—	—	Class A1 Common Shares	3,734,103	3,734,103	I
Series C Preferred^{F13,F6,F8,F14,F15,F5}	—	May 29, 2018	C	420,897	D	—	—	Class A1 Common Shares	420,897	0	I
Class A1 Common Shares^{F13,F6,F8,F14,F15}	—	May 29, 2018	C	420,897	A	—	—	Class A Common Shares	420,897	420,897	I
Series C Preferred^{F13,F7,F8,F14,F15,F5}	—	May 29, 2018	C	3,734,103	D	—	—	Class A1 Common Shares	3,734,103	0	I
Class A1 Common Shares^{F13,F7,F8,F14,F15}	—	May 29, 2018	C	3,734,103	A	—	—	Class A Common Shares	3,734,103	3,734,103	I
Series B Preferred^{F13,F6,F10,F14,F15,F9}	—	May 29, 2018	C	313,621	D	—	—	Class A1 Common Shares	313,621	0	I
Class A1 Common Shares^{F13,F6,F10,F14,F15}	—	May 29, 2018	C	313,621	A	—	—	Class A Common Shares	313,621	734,518	I
Series B Preferred^{F13,F7,F10,F14,F15,F9}	—	May 29, 2018	C	3,284,771	D	—	—	Class A1 Common Shares	3,284,771	0	I
Class A1 Common Shares^{F13,F7,F10,F14,F15}	—	May 29, 2018	C	3,284,771	A	—	—	Class A Common Shares	3,284,771	7,018,874	I
Series A Preferred^{F13,F6,F12,F14,F15,F11}	—	May 29, 2018	C	1,399,516	D	—	—	Class B1 Common Shares	1,399,516	0	I
Class B1 Common Shares^{F13,F6,F12,F14,F15}	—	May 29, 2018	C	1,399,516	A	—	—	Class A Common Shares	1,399,516	1,399,516	I
Series A Preferred^{F13,F7,F12,F14,F15,F11}	—	May 29, 2018	C	14,658,102	D	—	—	Class B1 Common Shares	14,658,102	0	I
Class B1 Common Shares^{F13,F7,F12,F14,F15}	—	May 29, 2018	C	14,658,102	A	—	—	Class A Common Shares	14,658,102	14,658,102	I

Explanation of responses

F1667, L.P. ("667") and Baker Brothers Life Sciences, L.P. ("Life Sciences", and together with 667, the "Funds") purchased 299,403 and 2,700,597 Class A common shares of Kiniksa Pharmaceuticals, Ltd. (the "Issuer"), respectively, for $18.00 per share pursuant to the Issuer's initial public offering that closed on May 29, 2018.
F10Represents conversion of the Issuer's Series B Convertible Preferred shares into Class A1 common shares as per the election of the Adviser upon the closing of the initial public offering of the Issuer. Class A1 common shares are subject to a beneficial ownership limitation, convertible at any time at the election of the holder on a 1 for 1 basis into Class A common shares. The Class A1 common shares have no expiration date. Each Class A1 common share automatically converts into one Class A common share upon transfer, except for transfers to or between affiliated holders.
F11Series A Convertible Preferred Shares of the Issuer ("Series A Preferred") convert on a 1 for 1 basis (the "Series A Conversion Ratio") into Class B1 common shares of the Issuer as per the election of the Adviser at anytime and automatically convert at the Series A Conversion Ratio upon the closing of the Issuer's initial public offering. The Series A Preferred have no expiration date.
F12Represents conversion of the Issuer's Series A Preferred shares into Class B1 common shares as per the election of the Adviser at the Series A Conversion Ratio upon the closing of the initial public offering of the Issuer. Class B1 common shares are, subject to a beneficial ownership limitation, convertible at the election of the holder on a 1 for 1 basis into either Class B common shares or Class A common shares. The Class B1 common shares have no expiration date. Each Class B1 common share automatically converts into one Class A common share upon transfer, except for transfers to or between affiliated holders.
F13Pursuant to Instruction 4(c)(iii), this response has been left blank.
F14The Adviser serves as the Investment Adviser to the Funds. In connection with the services provided by the Adviser, the Adviser receives an asset-based management fee that does not confer any pecuniary interest in the securities held by the Funds. Baker Bros. Advisors (GP) LLC (the "Adviser GP") is the Adviser's sole general partner. Julian C. Baker and Felix J. Baker are principals of the Adviser GP. The Adviser has complete and unlimited discretion and authority with respect to the investment and voting power of the securities held by the Funds. The general partners of the Funds relinquished to the Adviser all discretion and authority with respect to the investment and voting power of the securities held by the Funds.
F15Julian C. Baker, Felix J. Baker, the Adviser GP and the Adviser disclaim beneficial ownership of the securities held directly by the Funds except to the extent of their pecuniary interest therein, and this report shall not be deemed an admission that any of Julian C. Baker, Felix J. Baker, the Adviser GP or the Adviser is a beneficial owner of such securities for purposes of Section 16 or any other purpose.
F2After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Biotech Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in the Issuer's Class A common shares reported in column 5 of Table I that are directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.
F3After giving effect to the transaction reported herein, and as a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in the Issuer's Class A common shares reported in column 5 of Table I that are directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.
F4On February 9, 2018, 667 and Life Sciences purchased 420,897 and 3,734,103 Series C Convertible Preferred shares ("Series C Preferred") of the Issuer, adjusted for a 2.73235 for 1 reverse split on May 11, 2018, respectively, for $15.64 per share in a private financing.
F5Series C Preferred will convert on a 1 for 1 basis (the "Series C Conversion Ratio") into Class A1 common shares of the Issuer as per the election of Baker Bros. Advisors LP (the "Adviser") at any time and automatically convert at the Series C Conversion Ratio upon the closing of the Issuer's initial public offering. The Series C Preferred have no expiration date.
F6After giving effect to the transactions reported herein, and as a result of their ownership interest in Baker Biotech Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in securities reported in column 9 of Table II directly held by 667, a limited partnership of which the sole general partner is Baker Biotech Capital, L.P., a limited partnership of which the sole general partner is Baker Biotech Capital (GP), LLC, due to Baker Biotech Capital, L.P.'s right to receive an allocation of a portion of the profits from 667.
F7After giving effect to the transactions reported herein, and as a result of their ownership interest in Baker Brothers Life Sciences Capital (GP), LLC, Julian C. Baker and Felix J. Baker may be deemed to have an indirect pecuniary interest in the Issuer's securities reported in column 9 of Table II directly held by Life Sciences, a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital, L.P., a limited partnership of which the sole general partner is Baker Brothers Life Sciences Capital (GP), LLC, due to Baker Brothers Life Sciences Capital, L.P.'s right to receive an allocation of a portion of the profits from Life Sciences.
F8Represents conversion of the Issuer's Series C Preferred Shares into Class A1 common shares as per the election of the Adviser at the Series C Conversion Ratio upon the closing of the initial public offering of the Issuer. Class A1 common shares are, subject to a beneficial ownership limitation, convertible at any time at the election of the holder on a 1 for 1 basis into Class A common shares. The Class A1 common shares have no expiration date. Each Class A1 common share automatically converts into one Class A common share upon transfer, except for transfers to or between affiliated holders.
F9Series B Convertible Preferred Shares of the Issuer ("Series B Preferred") convert into the Issuer's Class A1 common shares on a 1 for 1 basis (the "Series B Conversion Ratio") as per the election of the Adviser at any time and automatically convert at the Series B Conversion Ratio upon the closing of the Issuer's initial public offering. The Series B Preferred have no expiration date.

Remarks

Felix J. Baker, a principal and Dr. Stephen R. Biggar, a full-time employee of Baker Bros. Advisors LP are directors of Kiniksa Pharmaceuticals, Ltd. (the "Issuer"). By virtue of their representation on the Board of Directors of the Issuer, for purposes of Section 16 of the Securities Exchange Act of 1934, as amended, the reporting persons are deemed directors by deputization of the Issuer.